The defining characteristic of functional amblyopia is deficient spatial resolution, this deficiency being most evident at moderate to high photopic luminance levels. This fact, along with other evidence, has provided the basis for suggesting that central mechanisms are responsible for the acuity deficit. At the same time, however, it is generally agreed that one of the major factors limiting acuity in the scotopic system is the coarseness of the neural grain in the peripheral retina. Several lines of evidence indicate that the amblyopic central retina resembles the normal peripheral retina, therby suggesting possible retinal involvement. The proposed research is designed to investigate the integrity of retinal mechanisms functional in amblyopia with specific reference to spatial information processing. Initially Crawford's equivalent-background under white light conditions and during both the early (primarily neural) and late phases of photopic dark-adaptation. For the normal eye, the principle of adaptive equivalence holds under scotopic conditions, but not under the photopic conditions selected for this experiment; i.e., it will not be possible to specify the adaptive state of the eye independently of the size of the test flash used to measure dark adaptation. A comparison of the equivalent background transformation applied to the normal and amblyopic eyes will indicate the extent to which the retinal mechanisms controlling spatial integration in the amblyopic central retina have a functional organization similar to that of the normal peripheral retina. Secondly, the counter-phased grating technique developed by Riggs & co-workers will be used to determine the effects of spatial variations within the stimulus field (i.e., bar width) on the photopic ERG evoked in the normal and the amblyopic eyes. Both types of experiments have been selected with a single purpose in mind--evaluating the contribution of retinal mechanisms to functional amblyopia.